This Core will perform cell isolations and culture procedures for investigators in Projects 2, 3, and 4. The Core will be responsible for isolating and maintaining cardiac myocytes, isolating and maintaining Xenopus laevis oocytes, and carrying out either cytoplasmic injections of mRNA or nuclear injections of DNA provided by the Molecular Biology Core (Core B). Projects 2 and 3 both propose studies of human and rat potassium channels expressed in mouse Ltk cells; this Core will assume the responsibility of growing and maintaining these cultures after the initial transfections have been performed in Core B. By centralizing these routine laboratory functions, resources (investigator effort, animal numbers and costs) will be used more effectively.